System and method of current shaping control for retract
AssigneeTexas Instruments Incorporated
InventorsJulio Enrique Ayala, II, Juergen Luebbe
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Abstract
A system for implementing current shaping for retract of a voice coil motor (VCM) includes drive circuitry coupled to drive the VCM according to a logic state of the system. Current shaping circuitry is configured to temporarily decrease the bandwidth of a VCM transconductance loop in response to a control signal. The transconductance loop includes at least the VCM, the current shaping circuitry and the drive circuitry. The system also includes logic configured to provide the control signal at an end portion a drive logic state to enter a current shaping logic state as a transition from the drive logic state to a floating logic state to reduce current through the VCM such that acoustic emissions from the VCM are mitigated during the retract.
Claims20
A system for performing retract of a voice coil motor (VCM), the system comprising:
- drive circuitry coupled to drive the VCM according to an operating logic state of the system;
- current shaping circuitry that includes a switch coupled in parallel with a current shaping resistor, and wherein the current shaping circuitry, wherein the current shaping circuitry is configured to temporarily decrease bandwidth of a VCM transconductance loop in response to a control signal, and wherein the VCM transconductance loop including at least the VCM, and wherein the current shaping circuitry and the drive circuitry, and wherein the switch being operated in response to the control signal to modify the bandwidth of the VCM transconductance loop;
- and
- logic configured to provide the control signal at an end portion a drive logic state to enter a current shaping logic state as a transition from the drive logic state to a floating logic state to reduce current through the VCM such that acoustic emissions from the VCM are mitigated during the retract.
A system for reducing acoustic noise of a VCM during retract, the system comprising:
- control logic configured to control an operating state of the VCM during a substantially constant velocity retract in one of a drive state, a current shaping state and a floating state;
- and
- current shaping circuitry that includes a switch connected in parallel with a current shaping resistor, wherein the current shaping circuitry is configured to temporarily decrease bandwidth of a VCM transconductance loop during the current shaping state, and wherein the control logic providing the current shaping state at a transition from the drive state to the floating state such that current through the VCM decays to about zero during the current shaping state, and wherein the switch being operated in during the current shaping state to modify the bandwidth of the VCM transconductance loop.
An apparatus comprising:
- a VCM;
- a sensor that is coupled to the VCM;
- a controller having:
- a sense amplifier that is coupled to the sensor;
- an error amplifier;
- a drive circuit that is coupled to the error amplifier and the VCM;
- a plurality of resistors coupled in series with one another between sense amplifier and the error amplifier;
- a switch that is coupled in parallel with at least one of the plurality of resistors;
- and
- logic that is configured to actuate the switch to adjust acoustic emissions from the VCM.
Dependencies are inferred from the claim text.